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PICList Thread
'opacity meter'
1998\04\11@214418 by PHXSYS

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Hello everyone!

I want to build an opacity meter to check discoloration in a liquid solution.
New fluid is relatively clear, but as it degrades over time it turns darker in
varying stages. I thought of using an infrared sender and receiver, but I've
never used one and need some help getting started. Any help ideas, sample code
or a "point in the right direction" would be greately appreciated..

Thanks in advance

Jon

1998\04\11@224033 by Michael Hagberg

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texas instruments makes a chip for this, it's an 8 pin device. i know that
it is being used in dishwaters to sense how dirty the water is. check out
their site.

michael


{Original Message removed}

1998\04\11@234203 by D. F. Welch

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At 09:41 PM 4/11/98 EDT, you wrote:
>Hello everyone!

Jon,
  IR may not be your best choice.  What you are describing
as a darkening is relative to visible light.  in the
Infra Red transparent materials may appear opaque and opaque
materials transparent.  To use Infrared you need to know the
wavelength of your emitter and the behavior of your fluid at that
wavelength.
>
>I want to build an opacity meter to check discoloration in a liquid solution.
>New fluid is relatively clear, but as it degrades over time it turns
darker in
>varying stages. I thought of using an infrared sender and receiver,
<snip>

>
>Thanks in advance
>
>Jon


-Dan
spam_OUTamersciTakeThisOuTspamflash.net

1998\04\12@172249 by Andy Kunz

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>I want to build an opacity meter to check discoloration in a liquid solution.
>New fluid is relatively clear, but as it degrades over time it turns
darker in
>varying stages. I thought of using an infrared sender and receiver, but I've

If you are working with nitric acid (sure sounds like it) there are other
considerations as well.  You would do better with spectral absorption
analysis.

Let's go private if you are working with acids (my father runs mfg for an
ultra-pure chem co (Puritan), my brother makes the RFNA for them, and I can
get the info from them pretty easily - shoot, they might want you to make
something along the same lines).

Andy

==================================================================
                    Andy Kunz - Montana Design
         Go fast, turn right, and keep the wet side down!
==================================================================

1998\04\12@182523 by XYGAX

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There is a simple method that comes to mind.........

Try a light bulb and a Cadnimum Sulphide cell  (ORP12) and measure the
conducted light through a sample. The CDS cell gets lower in resistance with
increasing light and if I remember corectly they arent very linier

Its simple but it depends on the sort of accuracy u are looking 4..

Cheers Steve.........

1998\04\13@020545 by Sean Breheny

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At 08:35 AM 4/12/98 -0400, you wrote:
>>I want to build an opacity meter to check discoloration in a liquid
solution.
>>New fluid is relatively clear, but as it degrades over time it turns
>darker in
>>varying stages. I thought of using an infrared sender and receiver, but I've
>
>If you are working with nitric acid (sure sounds like it) there are other
>considerations as well.  You would do better with spectral absorption
>analysis.
>
>Let's go private if you are working with acids (my father runs mfg for an
>ultra-pure chem co (Puritan), my brother makes the RFNA for them, and I can
>get the info from them pretty easily - shoot, they might want you to make
>something along the same lines).
>
>Andy

Andy and anyone else who might be able to answer this:

I am just a bit curious as to what kind of light source they use in
spectrophotometers. I have played with one, and it has a rotary dial which
can select any monochromatic wavelength from one end of the visible
spectrum to the other. The whole device was only about 2 feet by 1 foot by
8 inches. Seems like a pretty amazing light source in there! Cost about
$5000, though!

(For anyone not familiar with spectrophotometers, they are devices which
measure the absorbtion/transmission spectrum of a chemical sample)

Sean

+--------------------------------+
| Sean Breheny                   |
| Amateur Radio Callsign: KA3YXM |
| Electrical Engineering Student |
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1998\04\13@060236 by Steve Baldwin

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> I am just a bit curious as to what kind of light source they use in
> spectrophotometers. I have played with one, and it has a rotary dial which
> can select any monochromatic wavelength from one end of the visible
> spectrum to the other. The whole device was only about 2 feet by 1 foot by
> 8 inches. Seems like a pretty amazing light source in there! Cost about
> $5000, though!

The light source itself is a light bulb, not much different from one
in a flashlight.
Remember those experiments you did at school with a light, a few
lenses, a slit and a prism ? If you imagine a slit after the prism
and  the knob turning the prism, then you can select the wavelength
of light you want.
In an adjustable spectrophotometer, the prism is replaced with a
diffraction grating which consists of a lot of fine lines on a flat,
reflective surface. It has the same effect but the spectrum can be
spread further in less space than a prism would need and they cost
more to make. You can see the effect on CDROMs which have similarly
spaced lines on a reflective surface.

Steve.




======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: stevebspamKILLspamtla.co.nz      fax +64 9 820-1929
======================================================

1998\04\13@062556 by Andy Kunz

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>I am just a bit curious as to what kind of light source they use in

It depends on what you're testing for.  My brother did one when he worked
at a waste treatment plant (motto - "Waste is a terrible thing to mind")
using UV from a halogen bulb, I believe, to measure bioactivity (bugs).

Andy

==================================================================
                    Andy Kunz - Montana Design
         Go fast, turn right, and keep the wet side down!
==================================================================

1998\04\13@084828 by Mcorio

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In a message dated 98-04-11 21:44:28 EDT, you write:

<< I want to build an opacity meter to check discoloration in a liquid
solution.
New fluid is relatively clear, but as it degrades over time it turns darker
in
varying stages. I thought of using an infrared sender and receiver, but I've
never used one and need some help getting started. Any help ideas, sample
code
or a "point in the right direction" would be greately appreciated..
 >>

Before going too far, you should check that the change in color also occurs at
infrared wavelengths. Just because the visible color changes does not mean the
IR will. Also, it may change only at one "color". For example, it may start
nearly clear and get a darker and darker blue with little or no change at
other wavelengths (colors). Make sure you measure at the wavelength(s) that
change.

Mark A. Corio
Rochester MicroSystems, Inc.
200 Buell Road, Suite 9
Rochester, NY  14624
Tel: 716-328-5850
Fax: 716-328-1144
http://www.frontiernet.net/~rmi/
****** Designing Electronics for Research and Industry ******

1998\04\13@095123 by John Shreffler

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part 0 599 bytes
-----Original Message-----
From:   PHXSYS [SMTP:.....PHXSYSKILLspamspam.....AOL.COM]
Sent:   Saturday, April 11, 1998 9:42 PM
To:     EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU
Subject:        opacity meter

Hello everyone!

I want to build an opacity meter to check discoloration in a liquid solution.
New fluid is relatively clear, but as it degrades over time it turns darker in
varying stages. I thought of using an infrared sender and receiver, but I've
never used one and need some help getting started. Any help ideas, sample code
or a "point in the right direction" would be greately appreciated..

Thanks in advance

Jon

1998\04\13@130334 by Philip Starbuck

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>Hello everyone!
>
>I want to build an opacity meter to check discoloration in a liquid solution.
>New fluid is relatively clear, but as it degrades over time it turns darker in
>varying stages. I thought of using an infrared sender and receiver, but I've
>never used one and need some help getting started. Any help ideas, sample code
>or a "point in the right direction" would be greately appreciated..
>
>Thanks in advance
>
>Jon


The part numbers for the Texas Instruments Llgit to Frequency Converters are:

TSL230(A)(B)    Programmable Light-to-Frequency Converters
               http://www.ti.com/sc/docs/psheets/abstract/datasht/soes007b.htm

TSL235          Light-to-Frequency Converter
               http://www.ti.com/sc/docs/psheets/abstract/datasht/soes012.htm

TSL245          Infrared Light-to-Frequency Converter
               http://www.ti.com/sc/docs/psheets/abstract/datasht/soes018.htm


cheers,

Phil


Philip Starbuck
(909) 792-7917

"There are three principal ways to lose money.  Wine, women, and engineers.
While the first two are more pleasant the third is by far the more certain."
                                               -- Baron Rothschild
                                                       ca. 1860

1998\04\13@132440 by Reginald Neale

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Echoing Mark Corio's suggestion, you should do some experimenting to
determine if there is a spectral region that is uniquely affected by the
"discoloration." Also, the design of the optical system for collecting the
transmitted light may be important. Suspended particulates will scatter
light; dissolved materials may not. A "specular" system which tends to
reject scattered light, along with an optical filter centered on a
particularly sensitive wavelength, might give you results that are very
specific to the sort of degradation you are interested in.

Hardware-wise, that would still be quite easy to implement. You would need
an inexpensive incandescent source, an appropriate filter, perhaps a couple
of lenses, and one of the TI chips, which is very easy to interface with a
PIC.

Reg Neale

1998\04\18@093108 by Larry G. Nelson Sr.

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Typiaclly they use a white light and send it thru a prism to break it into
colors. By moving a slit in the path of the output "rainbow" you can pick
the color you want and use that for the specific source. They rely on
specific color temperature lamps and calibrations to compensate for lamp
life etc. I worked on some alternative systems to that.

At 02:05 AM 4/13/98 -0400, you wrote:

{Quote hidden}

Larry G. Nelson Sr.
@spam@L.NelsonKILLspamspamieee.org
http://www.ultranet.com/~nr

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